The present invention relates to an apparatus and method for directly installing a shut-off valve in a flowing oil well casing and, more particularly, to such an apparatus and method for shutting off a flowing oil well having concentric production casings and subsequently selectively and separately reopening each of said casings to recommence their respective flows.
Apparatus and methods for handling oil well blow-outs and fires are well known in the art. One of the most common devices used to control a well is a blow-out preventer (BOP). A BOP or an array of BOPs are attached directly to the wellhead and operate to rapidly close an open well hole or the space between the casing and the drill pipe to prevent the escape of pressurized oil or gas. These devices work essentially as plugs and may be either insertable laterally into the casing (ram type BOP) or expandable radially to fill the casing (annular BOP). On a land well, the BOP is normally located at the ground surface and, in a subsea well, at the ocean floor.
Although blow-out preventers are effective in preventing blow-outs and ensuing fires, if the wellhead is damaged or if a fire occurs before the blow-out preventers operate to seal the well, BOPs may become largely ineffective. Once a well is out of control or on fire, resort must be made to other means to bring the well under control.
Various types of relatively unsophisticated, brute force methods are employed to control wild wells, including those which may be on fire. All of these methods operate essentially directly at the wellhead to attempt to cap and seal it off. Obviously, if the well is afire, greater difficulty and hazards must be faced.
U.S. Pat. No. 1,879,160 discloses a method and apparatus for shutting off a burning oil well by plugging the same from an access point below ground. The apparatus inserts a wedge-like plug laterally through a hole drilled in the production pipe (and outer casing, if present) to plug the pipe and seal off the flow. Mud and cement are then pumped into the pipe through the plug to seal off the well. This method and apparatus contemplates permanent sealing of the well and taking the same completely out of production.
The prior art also discloses various types of apparatus for installing a plug in a flowing high pressure pipeline which plug can be subsequently withdrawn and reseated as a fully operative valve. Each of these patents utilizes means to cut a hole through or cut a section out of the flowing pipeline while withstanding the pressure therein and then permanently placing the valve in position.
U.S. Pat. No. 3,699,996 shows an apparatus including a drilling and reaming tool to cut a cylindrical hole through the flowing pipeline using a powered rotational drive and an axial hydraulic ram. A valve seat and valve plug are mounted axially behind the drill and the seat automatically snaps into position upon completion of the drilling and the drill bit can be subsequently removed from the valve plug. This apparatus requires complex sealing and locking components and requires that the drill bit be removed from the seat/plug assembly before the valve is operable.
U.S. Pat. No. 3,532,113 shows a combined cutting tool and gate valve which is used to cut a cylindrical hole laterally through the pipe and to close off the hole after cutting. The drill/gate may be subsequently withdrawn to open the valve, but the apparatus requires a complex variety of seals and packings to maintain a fluid tight valve.
U.S Pat. No. 4,552,170 shows a somewhat similar device, except that the drill which cuts a cylindrical hole through the pipe is followed axially by a tubular elastomeric seal which is radially expandable to seal the hole in response to axial compression imposed on the elastomer when the advancing cutting tool engages a stop after passing through the pipe.
U.S. Pat. No. 3,993,137 discloses an apparatus in which axially aligned and diametrically opposite drill and plug members are mounted in a confining saddle arrangement around an outer casing, and the interior pipe is immobilized by drills entering the pipe radially from different directions. A large drill is then used to cut through both the casing and the interior pipe, the drill is withdrawn, the drill access chamber closed, and a plug inserted from the diametrically opposite side to seal the casing. The plug is also capable of functioning as a valve. Means are also disclosed for maintaining operational flow of the well while it is plugged by diverting the flow through the plug. However, the two separate flows in the outer casing and interior pipe are mixed and cannot be separately diverted.
U.S. Pat. No. 4,516,598 also discloses a drill and a plug in axial alignment on diametrically opposite sides of the pipe. However, after a hole is drilled through the pipe, the drill is withdrawn, the mounting saddle rotated 180.degree., and the plug inserted into the hole to plug the pipe.
U.S. Pat. No. 4,108,194 shows a method and apparatus for providing a tapered pipeline seal in which a straight cylindrical hole is first drilled through the pipe and the cylindrical hole is then reamed to a taper adapted to receive a subsequently inserted tapered plug to seal the hole. However, no means are described for holding against pressure in a flowing pipe while drilling, reaming, or changing tools. The apparatus and method are only useful in plugging an empty pipeline.
Therefore, an apparatus and method which operates simply and effectively to seal off a flowing high pressure pipeline with a minimum of complex components would be most desirable. In particular, a device which utilizes the drilling and/or finishing tool as an integral part of the operating valve would be most desirable. In those well constructions utilizing an outer production casing and a smaller concentric interior production pipe, it would be most desirable to be able to plug the casing to halt flow of well fluids through both the casing and the pipe, but to be able to subsequently independently reopen the casing and the pipe and to separately divert the fluids flowing therein.
U.S. patent application Ser. No. 697,398, filed May 9, 1991, entitled "Directly Installed Shut-Off Valve Assembly for Flowing High Pressure Line", now the U.S. Pat. No. 5,076,311, and of common inventorship herewith discloses an apparatus for cutting into a flowing high pressure oil well casing using rotary drilling and finishing tools with the latter functioning in place as a plug and fully operable valve to subsequently reopen the well. The apparatus and method disclosed therein may be installed without adversely affecting the integrity of the production casing or subsequent operation of the well. However, that application does not address the problem of selectively reopening and separately diverting the fluid flows from each of the production casing and production pipe. In many wells, the fluids flowing in the production casing and the production pipe are somewhat or even completely different and, under normal operating conditions, the flows are maintained entirely separate. Therefore, it would be most desirable to be able to utilize the temporary plugging and valve means of the prior art to segregate the flows in the production casing and pipe to allow the well to function fully and effectively while plugged and while repairs to the wellhead are completed.